Dan,

I don't have any special knowledge, but I presume that columnar apples are made like most other apple trees. That is, by choosing an appropriate rootstock and then grafting a scion of the desired variety to it.

In the case of columnar, I believe the varieties were selected because they are genetically predisposed to grow up without much branching. Then they are pruned and trained to accentuate that trait.

I don't know if there are desireable columnar varieties that aren't under patent. It is certainly much easier to obtain scion wood from non-patented cultivars.

From another list:

"Wijik McIntosh, which is a columnar mutation. Like most apple varieties, it may well not be self-pollinating.
Siloam Orchards Nursery sells the tree and may have helpful info on care for you.
Here is what their catalog says: Mac Wijick (Colonade) - This is a form of McIntosh which grows vertically with a few vey upright branches. All the fruit is borne close to the trunk. Great for tight spaces or to grow vertically on a fence with your espalier trees. Zone 5. Grown on the M26 rootstock, but much smaller than other apples on M26, due to it's nature."

All columnar apples were bred from Wijik so they all have resemblance to Macintosh. They are easy to breed - cross a columnar apple with a regular one and half the seedlings will be columnar and can be picked out when they are only a few inches tall.